For what it's worth I had an older Suzuki 50 on a McKee Craft that was corroded so bad in places I was surprised it ran. The foot and midsection were beyond sanding and painting they were pitted so bad. If they're rusty on the outside they're sure rusty in the inside.

Saltwater will rust tupperware.

Dang..... hope mine doesnt get a hole in it.

Guy that did work on my motor said to spray down the head with CRC 656 (as well as any area that might corrode like trailer coupler, etc.) a couple times a year and it will make a big difference. Makes sense to me.

Suzuki Corrosion
 

OK, I looked at it today and got the scoop from the dealer. Here are some pix to show the problem area.
There is a plug in the port side of the "engine holder". This part is on DF90 thru DF140. The plug is ferrous metal in an aluminum housing that has hot exhaust behind it. It was intended as a potential place for service to install an O2 sensor which they ended up never using. The corrosion is from the inside out. Its not salt corrosion because there's no water there. Its bimetalic corrosion and clearly a defect in material or design. My guess is cheap chinese stainless steel plugs and some get lucky, some don't. Hence, Suzuki has stopped tapping/plugging the hole in newer models. I didn't ask what year. Mines's a 2004.
The dealer said he has seen it in 3 older engines. One was in a twin configuration with one motor badly corroded so they took the other apart and it was fine.
Estimated cost to repair $1800 ($1018 for parts). Hopefully he doesn't find corrosion in the head or oil pan.

By the way, I got the picture off The Hull Truth site where someone else had exact same problem but looks like a Johnson 'cause its white.

Did you see any signs of corrosion on the outside?

Before it broke thru and covered the engine in exhaust soot, you would have sworn it was a brand new engine. Of course, I have never removed the port side cover because the oil drain and filter are on the other side. Looking at the damage I think you might notice a rusty appearance to the steel plug but the aluminum corroded from inside out.
Do you risk removing the plug to take a look? If it is bad you ruin the aluminum housing and have to fix it now. If its good, you get peace of mind. Notice Suzuki isn't recommending it as maintenance...don't want to open cans of worms!
Going to try to pick up the V20 "sans motor" tomorrow if the 1/4 " of snow melts.
Good Luck.
C

Fuel line problem?
 

I would also consider replacing the fuel lines. My next door neighbor has a 115 Suzuki (2007, I think) and this past summer the fuel lines turned to stretchy "gummy Bears" with holes in them. We were fishing and suddenly the motor wouldn't start, then we smelled gas. Pulled the cowling and saw holes in the fuel line. Managed to cut out a section, re-route it and make it home. Must have been the ethanol they switched to the year before in this area. We were fortunate to make it home under our own power. The motor had been worked on previously, so maybe the stock fuel lines were replaced with something non-ethanol resistant then - we don't know.

Still, might be cheap insurance to replace them or carry spares!